Alfalfa's wide swings in RFV quality also affect the nutrient level in cattle rations. Having an accurate RFV measurement can help beef producers properly balance the amount of protein and energy needed for achieving production and profitability goals, Harvest Tec says.

Harvest Tec's system also measures moisture, bale weight and density to determine RFV.

Bales with greater density contain more leaves, because leaves pack much better than stems. A bale with high leaf content has higher feed value and, consequently, greater density. The leaf to stem ratio can be influenced by several factors. Leaves are flat, and compress nicely, adding weight to the bale. Bales with more stems will always weigh less. Stems are round and stiff, and do not pack as well.

How the Harvest Tec RFV calculator works
The producer takes a hay sample just before or after the field is cut, and gets a lab RFV analysis. That value is entered into the Harvest Tec system when baling begins. As the baler operates, Harvest Tec's wheel sensors take hay moisture readings 96 times every 3 seconds to achieve moisture measurement of plus or minus 1% accuracy.

Next, the baler's scale provides bale weight accuracy within 2 percentage points. From the moisture and weight data, the Harvest Tec system calculates the dry matter density and the relative feed value of each individual bale.

Harvest Tec RFV calculator system accuracy

Utah State University in Provo, Utah, completed a study on three cuttings of alfalfa. Nearly 550 harvested bales were individually cored and analyzed at the University's lab. The Harvest Tec system consistently tracked with the core sample analysis for each bale.

The new system also was tested on eight farms across six states, with more than 3,000 bales individually cored and analyzed. The research was done with baling in different temperatures, varieties and cuttings. It included both irrigated and non-irrigated fields, along with different makes of balers and bale sizes.

The comparative results demonstrated that the values measured by the Harvest Tec RFV calculator system closely follow the values from the lab coring analysis, Harvest Tec said.

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How the RFV calculation is recorded
During the baling process, the new system's processor displays the RFV on the monitor screen, and writes each bale's RFV and TDN to a job record that can later be printed out. It also determines average values for that job or field.

Harvest Tec's bale "tagger" then applies a vinyl tag containing an RFID chip to the twine on the bale. The tagger system writes valuable information to the tag including bale moisture, weight and relative feed value. It also records bale number, the time the bale was made, field location, and more.

The tag's recorded data can be read back using either a hand held scanner or one that mounts directly to bale handling machines. Some farms using the system scan the bales as they come out of the field, sorting them by RFV into low, medium and high quality groups. Sorting can also be done when the hay is stacked for feeding or as a truck is loaded. This way, hay producers and sellers can give the buyer precisely the hay quality he wants.

Harvest Tec's portal scanner will scan entire loads as the truck passes under it, reading the data directly into a computer. This makes it easy to sort bale loads, and for keeping track of inventory.

Randomly coring bales to determine RFV is being replaced by this new technology, Harvest Tec says.

"The precision farming way to determine and manage hay quality is to measure the whole bale at the time it is produced, tag it that way, ship it that way and feed it that way," the company says.